Glyphosate lessons: is biodegradation of pesticides a harmless process for biodiversity?

The historical perspective on the rapid biodegradation of pesticides as a mitigating factor in environmental risk assessment is reexamined through the example of glyphosate and its implications for freshwater biodiversity. Commonly employed standardized methods by national agencies for assessing the environmental risk of pesticides predominantly rely on single-species tests, overlooking the intricate nature of ecosystems. Glyphosate, one of the most widely used pesticides marketed for its purported rapid biodegradability, is often perceived as relatively innocuous. However, its degradation releases phosphorus into the environment, inducing a trophic state shift in water systems towards more eutrophic conditions, consequently affecting water quality. These findings highlight the cascading ecological repercussions of glyphosate biodegradation, driving the proliferation of specific aquatic organisms, such as picocyanobacteria and metaphyton, resulting in the alteration of ecosystem structure and dynamics. The study explores challenges posed by commercial pesticide formulations and investigates the consequences of pesticide interactions with specific anthropogenic factors. A case in point is the interaction of glyphosate with the invasive mussel Limnoperna fortunei, exacerbating the overall scenario. The ecological framework analyzed challenges the conventional notion that pesticide biodegradation is inherently a neutral or positive event. The results underscore the necessity of reassessing the role of biodegradation itself in environmental impact assessments for pesticides.